1. Field of the Invention
This invention relates to a magnetic disk cartridge employed for the purpose of recording and reproduction of voice, image and other such data. More particularly, this invention relates to an improved structure for affixing the magnetic disk of the cartridge to the rotational support means.
2. Description of the Prior Art
In recent years, in response to the demands of the information society, magnetic recording media have come into widespread use. The magnetic disk, in particular, is rapidly becoming very popular because it is simple and convenient to operate. Because it is extremely easy to randomly access magnetic disks, such disks are now playing an essential role as the recording media in small computers, word processors and other such office automation equipment. And still more recently such features of magnetic disks have caused them to become a focus of attention in a smaller form--the microfloppy disk--for use as the recording media of electronic still cameras (for example Sony Corp.'s "Mavica"). For handling and operational convenience these microfloppy disks are used in the form of a magnetic disk cartridge consisting of a casing within which is housed the disk, and a center core which supports the disk for the rotation thereof. This center core usually consists of a main core upon which is laid a resilient ring and an upper core, in that order, with the disk being pressed against the main core by one entire side of the resilient ring, so the disk is held by the surface frictional forces between it and the resilient ring.
With the above magnetic disk cartridge, however, the upper core pressing the resilient ring onto the disk can produce directional stresses where the ring contacts the disk, causing deformation of the disk.
When the core proper is ultrasonically welded to the upper core the ultrasonic vibration can make such deformation particularly noticeable.
If a disk is deformed the gap between the magnetic recording/reproduction head and the disk surface during recording/reproduction operations will be uneven, with a consequent deterioration in recording/reproduction characteristics.
In the case of microfloppy disks, even very slight deformation can facilitate the occurrence of data recording/reproduction errors.